System architecture for power control in an optical transmission line

ABSTRACT

An optical network is described that has a first ROADM node, a second ROADM node, and an optical transmission line establishing optical communication between the first ROADM node and the second ROADM node. The optical transmission line including an in-line amplifier node having a total input power and a total output power. The in-line amplifier node has a first monitoring tool configured to measure input optical power of the in-line amplifier node, and a second monitoring tool configured to measure output optical power of the in-line amplifier node. A software defined L0 network controller has circuitry configured to receive the optical power measured by the first and second monitoring tools from the in-line amplifier node, and to configure at least one of a gain and a gain tilt of the in-line amplifier node.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation patent application ofU.S. patent application Ser. No. 15/887,771, titled “Optical RestorationMethods in Optical Networks Controlled by a L0 SDN Controller”, filed onFeb. 2, 2018, which claims priority to the provisional patentapplications identified by, U.S. Ser. No. 62/453,519 titled “Layer-0Optical Power Controls by a Centralized SDN Controller” filed on Feb. 2,2017, U.S. Ser. No. 62/453,523 titled “External Network-to-NetworkInterface and Optical Express Power Controls” filed on Feb. 2, 2017,U.S. Ser. No. 62/453,525 titled “Optical Restoration Methods in OpticalNetworks Controlled by a L0 SDN Controller” filed on Feb. 2, 2017, U.S.Ser. No. 62/453,530 titled “System Architecture for Power Control in anOptical Transmission Line” filed on Feb. 2, 2017, and U.S. Ser. No.62/453,531 titled “Method of Control for the Maintenance of the OpticalPower in a ROADM Network” filed on Feb. 2, 2017, the entire contents ofwhich are hereby incorporated herein by reference.

FIELD OF THE DISCLOSURE

The disclosure generally relates to methods and apparatuses for recoveryin coherent optical transport networks (OTN) using a controller thatcontrols all nodes in a restore path, in a parallel fashion, for fasterrestoration of the restore path.

BACKGROUND

An Optical Transport Network (OTN) is comprised of a plurality of switchnodes linked together to form a network. The OTN includes a data layer,a digital layer, and an optical layer. The optical layer containsmultiple sub-layers. OTN structure, architecture, and modeling arefurther described in the International Telecommunication Unionrecommendations, including ITU-T G.709, ITU-T G.872, and ITU-T G.805,which are well known in the art. In general, the OTN is a combination ofthe benefits of SONET/SDH technology and dense wavelength-divisionmultiplexing (DWDM) technology (optics).

The construction and operation of switch nodes (also referred to as“nodes”) in the OTN is well known in the art. In general, the nodes ofan OTN are generally provided with a control module, input interface(s)and output interface(s). The control modules of the nodes in the OTNfunction together to aid in the control and management of the OTN. Thecontrol modules can run a variety of protocols for conducting thecontrol and management (i.e. Operation, Administration andMaintenance—referred to as OAM) of the OTN. One prominent protocol isreferred to in the art as Generalized Multiprotocol Label Switching(GMPLS).

Generalized Multiprotocol Label Switching (GMPLS) is a type of protocolwhich extends multiprotocol label switching (MLS) to encompass networkschemes based upon time-division multiplexing (e.g. SONET/SDH, PDH,G.709), wavelength multiplexing, and spatial switching (e.g. incomingport or fiber to outgoing port or fiber). Multiplexing is when two ormore signals or bit streams are transferred over a common channel.

Wave-division multiplexing is a type of multiplexing in which two ormore optical carrier signals are multiplexed onto a single optical fiberby using different wavelengths (that is, colors) of laser light.

Generalized Multiprotocol Label Switching (GMPLS) includes multipletypes of label switched paths including protection and recoverymechanisms which specify (1) working connections within a network havingmultiple nodes and communication links for transmitting data between aheadend node and a tail end node; and (2) protecting connectionsspecifying a different group of nodes and/or communication links fortransmitting data between the headend node to the tail end node in theevent that one or more of the working connections fail. Workingconnections may also be referred to as working paths. Protectingconnections may also be referred to as recovery paths and/or protectingpaths and/or protection paths. A first node of a path may be referred toas a headend node or a source node. A last node of a path may bereferred to as a tail end node or end node or destination node. Theheadend node or tail end node initially selects to receive data over theworking connection (such as an optical channel data unit label switchedpath) and, if a working connection fails, the headend node or tail endnode may select a protecting connection for passing data within thenetwork. The set up and activation of the protecting connections may bereferred to as restoration or protection.

Lightpaths are optical connections carried over a wavelength, end toend, from a source node to a destination node in an optical transportnetwork (OTN). Typically, the lightpaths pass through intermediate linksand intermediate nodes in the OTN. At the intermediate nodes, thelightpaths may be routed and switched from one intermediate link toanother intermediate link. In some cases, lightpaths may be convertedfrom one wavelength to another wavelength at the intermediate nodes.

As previously mentioned, optical transport networks (OTN) have multiplelayers including a data packet layer, a digital layer, and an opticallayer (also referred to as a photonic layer). The data and digitallayers include an optical channel transport unit (OTU) sub-layer and anoptical channel data unit (ODU) sub-layer. The optical layer hasmultiple sub-layers, including the Optical Channel (OCh) layer, theOptical Multiplex Section (OMS) layer, and the Optical TransmissionSection (OTS) layer. The optical layer provides optical connections,also referred to as optical channels or lightpaths, to other layers,such as the electronic layer. The optical layer performs multiplefunctions, such as monitoring network performance, multiplexingwavelengths, and switching and routing wavelengths. The Optical Channel(OCh) layer manages end-to-end routing of the lightpaths through theoptical transport network (OTN). The Optical Multiplex Section (OMS)layer network provides the transport of optical channels through anoptical multiplex section trail between access points. The OpticalTransmission Section (OTS) layer network provides for the transport ofan optical multiplex section through an optical transmission sectiontrail between access points. The OCh layer, the OMS layer, and the OTSlayer have overhead which may be used for management purposes. Theoverhead may be transported in an Optical Supervisory Channel (OSC).

The Optical Supervisory Channel (OSC) is an additional wavelength thatis adapted to carry information about the network and may be used formanagement functions. The OSC is carried on a different wavelength thanwavelengths carrying actual data traffic and is an out-of-band channel.Typically, the OSC is used hop-by-hop and is terminated and restarted atevery node.

The International Telecommunications Union (ITU) recommendation ITU-TG.709 further defines the OTS, OMS and OCh layers and recommends use ofthe OSC to carry overhead corresponding to the layers. Additionally,ITU-T recommendation G.872 specifies defects for the OTS, OMS, and OChlayers as well as specifying Operation, Administration & Maintenance(OAM) requirements.

ITU-T recommendations suggest that the OSC utilize a SynchronousTransport Signal (STS) Optical Carrier transmission rate OC-3. OpticalCarrier transmission rates are a standardized set of specifications oftransmission bandwidth for digital signals that can be carried on fiberoptic networks. The OC-3 frame contains three column-interleaved STSLevel 1 (STS-1) frames; therefore, the line overhead consists of anarray of six rows by nine columns (that is, bytes). The OC-3 frameformat is further defined in Telecordia's Generic Requirements GR-253,“Synchronous Optical Network Common Generic Criteria,” Issue 4. The OC-3frame format contains a transport overhead portion. Within the transportoverhead portion, bytes designated as D4, D5, D6, D7, D8, D9, D10, D11,and D12 are defined by GR-253 for use by Data Communication Channel(DCC).

The patent application identified by U.S. Ser. No. 13/452,413, titled“OPTICAL LAYER STATUS EXCHANGE OVER OSC—OAM METHOD FOR ROADM NETWORKS”filed on Apr. 20, 2012, discloses methods for supporting OAM functionsfor the optical layers, for example, for carrying defect information andoverhead in the OSC. The application discloses methodology andapparatuses for supporting OAM functions such as continuity,connectivity, and signal quality supervision for optical layers. Themethodology discloses mapping optical layer overhead OAM information tospecific overhead bits and assigning the overhead bits to specific OSCoverhead bytes. This provides reliable exchange of overhead bytes overOSC between nodes.

However, current systems and publications do not disclose mechanisms foroptical layer recovery (e.g. protection and/or restoration). Currentprotocols define mechanisms for supporting protection in digital layers(SDH, OTN Networks) such as GR-253 and G.873.1; however, optical nodesmay not have access to the digital layer. Further, there are noprotocols for supporting protection functions in optical layers (OMS &OCh layers).

In the past, restoration systems would detect and localize a failure,calculate a restore path (or select from a pre-calculated list ofrestore paths based upon preference), signal for the restore path todetermine whether the restore path was available, and then activate therestore path and manage optical power end to end. The activation of therestore path used a serial process in which nodes along the restore pathwere signaled in a serial manner due to distributed power controls. Thisrequires the head-end node to receive information and updates ofinformation from the nodes in the network, including each of the nodesin the restore path during the restoration process. Obtaining theinformation from the nodes in the network, and signaling and activatingthe nodes in a serial manner was a time-consuming process.

The present disclosure addresses these deficiencies utilizing acontroller that controls all nodes in a restore path, in a parallelfashion, for faster restoration of the restore path.

SUMMARY

Method and optical nodes are disclosed. The problems caused by thetime-consuming process of serial activation of optical nodes in arestore path are addressed by utilizing a controller that controls alloptical nodes in a restore path, in a parallel fashion, for fasterrestoration of the restore path.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more implementationsdescribed herein and, together with the description, explain theseimplementations. In the drawings:

FIG. 1 is an illustration of an exemplary optical transport network inaccordance with the present disclosure.

FIG. 2A is a block diagram of an aspect of an exemplary optical node inaccordance with the present disclosure.

FIG. 2B is a block diagram of a transmitter of the exemplary opticalnode of FIG. 2A.

FIG. 2C is a block diagram of a receiver of the exemplary optical nodeof FIG. 2B.

FIG. 3 is block diagram of another aspect of the exemplary node of FIG.2.

FIG. 4 is a block diagram of an exemplary SDN L0 Network Controllerconstructed in accordance with the present disclosure.

FIG. 5 is a flow diagram an exemplary monitoring and reporting processin accordance with the present disclosure.

FIG. 6 is an illustration of the exemplary optical transport network ofFIG. 1 in which a fault has occurred between a head end node and anintermediate node.

FIG. 7 is a flow diagram of an exemplary protection process foractivating a restore path in accordance with the present disclosure.

FIG. 8 is a block diagram of an exemplary L0 power controllerconstructed in accordance with the present disclosure.

FIG. 9 is a block diagram of interactions between constituent componentsof an SDN architecture optical network and an L0 power controller inaccordance with the present disclosure.

FIG. 10 is an illustration of an exemplary disaggregated optical node inaccordance with the present disclosure.

FIG. 11 is an illustration of an exemplary SDN architecture opticaltransport network in accordance with the present disclosure.

FIG. 12 is an illustration of another exemplary SDN architecture opticaltransport network in accordance with the present disclosure.

FIG. 13 is an illustration of an exemplary multi-domain SDN architectureoptical transport network in accordance with the present disclosure.

FIG. 14A is an illustration of an exemplary multi domain opticaltransport network with an external network to network interfaceinterconnecting a first degree node of a first domain and a seconddegree node of a second domain in accordance with the presentdisclosure.

FIG. 14B is an illustration of another exemplary multi domain opticaltransport network with an external network to network interfaceinterconnecting a first degree node of a first domain and an ILA of asecond domain in accordance with the present disclosure.

FIG. 14C is an illustration of an exemplary multi domain opticaltransport network with an external network to network interfaceinterconnecting a first ILA of a first domain and a second ILA of asecond domain in accordance with the present disclosure.

FIG. 15 is an illustration of an optical network segment having powerspectral density measuring points in accordance the present disclosure.

FIG. 16 is a block diagram illustrating exemplary interconnectionsbetween network elements in an optical network in accordance with thepresent disclosure.

FIG. 17 is a block diagram illustrating exemplary interconnectionsbetween network elements in an optical network in accordance with thepresent disclosure.

FIG. 18 is a block diagram illustrating exemplary interconnectionsbetween network elements in a multi-domain optical network in accordancewith the present disclosure.

FIG. 19 is an illustration of an exemplary optical transmission line ofan optical transport network in accordance with the present disclosure.

FIG. 20 is an illustration of a dependency matrix of an opticaltransport network in accordance with the present disclosure.

FIG. 21 is a block diagram illustrating an exemplary control loop statemachine in accordance with the present disclosure.

FIG. 22 is an illustration of an exemplary parameter flow in accordancewith the present disclosure.

FIG. 23 is an illustration of an exemplary ROADM node controller powercontrol state machine in accordance with the present disclosure.

FIG. 24 is an illustration of an exemplary transport line controllerpower control state machine in accordance with the present disclosure.

FIG. 25 is a block diagram illustrating an exemplary L0 power controllerorchestrating a sequence of control loops in accordance with the presentdisclosure.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings.The same reference numbers in different drawings may identify the sameor similar elements.

The mechanisms proposed in this disclosure overcome the problems causedby the time consuming nature for optical layer recovery. The presentdisclosure describes methods and apparatuses in which a SDN L0 networkcontroller receives near real-time network performance information fromeach of the optical nodes in a restore path, and then implementsrecovery mechanisms in a parallel manner to reduce the time involved inactivating a restore path.

DEFINITIONS

If used throughout the description and the drawings, the following shortterms have the following meanings unless otherwise stated:

DWDM stands for dense wavelength division multiplexing. DWDM multiplexesmultiple optical carrier signals, such as Optical Channel (OCh) signalsor Super Channel (SCh) signals, onto a single optical fiber by usingdifferent laser light wavelengths (colors).

FPGA stands for field programmable gate array. FPGAs can be programedafter deployment in a system.

GMPLS stands for Generalized Multi-Protocol Label Switching whichextends Multi-Protocol Label Switching to encompass time-division (forexample, SONET/SDH, PDH, G.709), wavelength (lambdas), and spatialmultiplexing (e.g., incoming port or fiber to outgoing port or fiber).The GMPLS framework includes a set of routing protocols which runs on acontrol module. The Generalized Multiprotocol Label Switchingarchitecture is defined, for example in RFC 3945.

LOS Stands for Loss of Signal.

LSP stands for Label Switched Path which is a path through a GeneralizedMulti-Protocol Label Switching network. Note that Label Switched Pathscan be bidirectional or unidirectional; they enable packets to be labelswitched through the Multiprotocol Label Switched network from a port onan ingress node (which can be called a headend node) to a port on anegress node (which can be called a tail end node).

MPLS stands for multi-protocol label switching which is a scheme intelecommunications networks for carrying data from one node to the nextnode. MPLS operates at an OSI model layer that is generally consideredto lie between traditional definitions of layer 2 (data link layer) andlayer 3 (network layer) and is thus often referred to as a layer 2.5protocol.

OAM stands for Operation, Administration and Maintenance. Examples ofOAM functions include continuity, connectivity and signal qualitysupervision.

OADM stands for optical add/drop multiplexer. ROADM stands forreconfigurable optical add/drop multiplexer. Network operators canremotely reconfigure the multiplexer by sending soft commands with aROADM.

OC stands for optical carrier. Optical carrier transmission rates are astandardized set of specifications of transmission bandwidths fordigital signals that can be carried on fiber optic networks.

OCh stands for Optical Channel layer.

OLT stands for Optical Line Terminal.

OMS stands for Optical Multiplex Section layer.

OSC stands for Optical Supervisory Channel.

OTN stands for Optical Transport Network which includes a set of opticalswitch nodes which are connected by optical fiber links. ITU-Trecommendations G.709 and G.872 define OTN interface requirements andnetwork architecture respectively.

OTS stands for Optical Transmission Section layer.

SCh stands for Super Channel. A Super-Channel (SCh) is a collection ofone or more frequency slots to be treated as a unified entity formanagement and control plane purposes. A Frequency Slot is a range offrequency allocated to a given channel and unavailable to other channelswithin the same flexible grid. A frequency slot is a contiguous portionof the spectrum available for an optical passband filter. A frequencyslot is defined by its nominal central frequency and its slot width. Afrequency slot is further defined in the InternationalTelecommunications Union Recommendation ITU-T G.694.1, “Spectral gridsfor WDM applications: DWDM frequency grid”. A contiguous spectrumSuper-Channel is a Super-Channel with a single frequency slot. Asplit-spectrum Super-Channel is a Super-Channel with multiple frequencyslots.

SDN stands for Software defined networking. SDN, as used herein,includes software, which may be executed by hardware that is separatefrom switch nodes within the optical transport network, and whichincludes the functionality to compute and provision paths through theoptical transport network for multiple switch nodes as well as instructone or more switch nodes to compute paths through the optical transportnetwork.

SF stands for Signal Failure.

SONET/SDH stands for Synchronous Optical Networking/Synchronous DigitalHierarchy which are standardized multiplexer protocols that transfermultiple digital bit streams over optical fiber using lasers or lightemitting diodes.

DESCRIPTION

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a nonexclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by anyone of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the inventive concept. Thisdescription should be read to include one or more and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Throughout this application, the term “about” is used to indicate that avalue includes the inherent variation of error for the quantifyingdevice, the method being employed to determine the value, or thevariation that exists among the study subjects. For example, but not byway of limitation, when the term “about” is utilized, the designatedvalue may vary by plus or minus twelve percent, or eleven percent, orten percent, or nine percent, or eight percent, or seven percent, or sixpercent, or five percent, or four percent, or three percent, or twopercent, or one percent.

The use of the term “at least one” or “one or more” will be understoodto include one as well as any quantity more than one, including but notlimited to, 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The term“at least one” or “one or more” may extend up to 100 or 1000 or moredepending on the term to which it is attached. In addition, thequantities of 100/1000 are not to be considered limiting, as lower orhigher limits may also produce satisfactory results.

In addition, the use of the phrase “at least one of X, V, and Z” will beunderstood to include X alone, V alone, and Z alone, as well as anycombination of X, V, and Z.

The use of ordinal number terminology (i.e., “first”, “second”, “third”,“fourth”, etc.) is solely for the purpose of differentiating between twoor more items and, unless explicitly stated otherwise, is not meant toimply any sequence or order or importance to one item over another orany order of addition.

As used herein, any reference to “one embodiment,” “an embodiment,”“some embodiments,” “one example,” “for example,” or “an example” meansthat a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearance of the phrase “in some embodiments” or “oneexample” in various places in the specification is not necessarily allreferring to the same embodiment, for example.

In accordance with the present disclosure, messages transmitted betweennodes can be processed by circuitry within the input interface(s),and/or the output interface(s) and/or the node controller. Circuitrycould be analog and/or digital, components, or one or more suitablyprogrammed microprocessors and associated hardware and software, orhardwired logic. Also, certain portions of the implementations have beendescribed as “components” that perform one or more functions. The term“component,” may include hardware, such as a processor, an applicationspecific integrated circuit (ASIC), or a field programmable gate array(FPGA), or a combination of hardware and software. Software includes oneor more computer executable instructions that when executed by one ormore component cause the component to perform a specified function. Itshould be understood that the algorithms described herein are stored onone or more non-transitory memory. Exemplary non-transitory memoryincludes random access memory, read only memory, flash memory or thelike. Such non-transitory memory can be electrically based or opticallybased. Further, the messages described herein may be generated by thecomponents and result in various physical transformations. Additionally,it should be understood that the node can be implemented in a variety ofmanners as is well known in the art.

An exemplary optical transport network (OTN) 20 is shown in FIG. 1, byway of example. The optical transport network 20 includes optical switchnodes 22A-22 n (hereinafter referred to as “nodes” or “optical nodes” or“photonic nodes”) and a SDN L0 network controller 24 communicating withthe nodes 22A-22 n in parallel via a network 26. The SDN L0 NetworkController 24 collects network topology information internal to at leastsome of the nodes 22A-22 n, as well as optical layer network performanceinformation from the nodes 22A-22 n. Exemplary optical layer networkperformance information includes optical amplifier gains, amplifiertilt, amplifier noise figure, span loss, component attenuations andattenuation set points for variable optical attenuators, + optical powerlevels at all interfaces, optical switch configurations (of e.g. WSS ormulti-cast switch), alarms. The SDN L0 network controller 24 utilizesthe network topology information to compute L0 paths, set up the L0paths, and activate/deactivate the L0 paths. To obtain networkconfiguration information and network performance information, set upthe paths, and/or activate/deactivate the paths the SDN L0 networkcontroller 24 may communicate messages directly with the nodes 22A-22 nvia the network 26 in a parallel manner.

The optical transport network 20 may conform to the requirements of theOSI model view of networks having seven layers, i.e., layer 1—physicallayer; layer 2—data link layer; layer 3—network layer; layer 4—transportlayer; layer 5—session layer; layer 6—presentation layer; and layer7—application layer. In addition, the optical transport network 20 hasan optical layer (denoted herein by “L0”) that is a server layer thatprovides services to other layers, including lightpaths to a variety ofclient layers. In other words, the other layers within the OSI modelmake use of the lightpaths provided by the optical layer. To a SONET,Ethernet or IP network operating over the optical layer, the lightpathsare simply replacements for hardwired fiber connections between SONETterminals or IP routers. A lightpath is a connection between two nodesin the network, and is set up by assigning a dedicated wavelength oneach link in the lightpath. The optical layer multiplexes multiplelightpaths into a single fiber and allows individual lightpaths to beextracted efficiently from the composite multiplex signal at networknodes 22A-22E, for example. This lightpath can be set up or taken downin response to a request from a higher layer. The optical transportnetwork 20 may include any number of optical nodes 22A-22 n. Forexemplary purposes, the optical transport network 20 of FIG. 1 includesfive optical nodes 22A-22E. The optical transport network 20 may beconfigured in any topology, for example, linear, ring, or mesh.

A headend node and a tail end node may be denoted for a particular pathin accordance to the path setup direction. In this example, optical node22A functions as a headend node (also known as a source node); whileoptical node 22C functions as a tail end node (also known as adestination node). Other optical nodes 22 between the headend node 22Aand tail end node 22C in a particular path are known as intermediatenodes. In this example, the optical nodes 22B, 22D, and 22E act asintermediate nodes. In between the optical nodes 22A-22 n arecommunication links 30A-30 m. For purposes of simplicity of explanation,communication links 30A-30G are illustrated in FIG. 1, but it will beunderstood that there may be more or fewer communication links 30.

The optical nodes 22A-22 n are adapted to facilitate the communicationof data traffic (which may be referred to herein as “traffic” and/or“data”) between optical nodes 22A-22 n in the optical transport network20 over communication links 30A-30 m, as well as into and out of theoptical transport network 20.

The communication links 30 can be implemented in a variety of ways, suchas an optical fiber or other waveguide carrying capabilities. Thecommunication links 30 can be fiber optic cables.

Data traffic and control information may follow one or more pathsthrough the optical transport network 20. A primary path 34 (forexample, OCh #1) may be established by one or more optical nodes 22A-22n, or by the SDN L0 network controller 24 separate from the opticalnodes 22A-22 n and/or separate from the optical transport network 20. Inthe example shown in FIG. 1, the primary path 34 is established betweenheadend node 22A and tail end node 22C through intermediate node 22B.The primary path 34 initially carries data traffic and controlinformation, and continues to carry data traffic and control informationwhile there is no failure on the primary path 34.

A restoration path 36 (for example, OCh #1) may also be established tocarry data traffic and control information. The headend node 22A and thetail end node 22C may select data traffic from the restoration path 36if there is a failure on the primary path 34. In FIG. 1, the restorationpath 36 is illustrated between headend node 22A and tail end node 22Cthrough intermediate nodes 22D and 22E.

The primary path 34 and the restoration path 36 can be established byone or more nodes 22A-22 n, such as headend node 22A, prior to anyfailure in the optical transport network 20, as illustrated in FIG. 1.Additionally, or alternately, one or more restoration path 36 may beestablished after a failure in the optical transport network 20 (seeFIGS. 5 and 7). The primary path 34 and the restoration path 36 may beestablished, for example, by using GMPLS protocols. The primary path 34and the restoration path 36 may be bi-directional or co-routed.

In general, the term “dedicated protection,” as used herein, refers to asituation in which the headend node 22A or tail end node 22C sets up adedicated restoration path 36 for a particular primary path 34, asillustrated in FIG. 1, in case of failure of the primary path 34, beforefailure of the primary path 34. In dedicated protection, the datatraffic is simultaneously transmitted from the headend node 22A (and/ortail end node 22C) on both the primary path 34 and restoration path 36.Dedicated protection may be used with unidirectional and bidirectionalprotection, as described in RFC 4872, “RSVP-TE Extensions for E2E GMPLSRecovery” (May 2007).

Referring to FIGS. 2A, 2B, 2C, and 3, shown therein are block diagramsof aspects of an exemplary optical node 22A constructed in accordancewith the present disclosure. In general, the optical nodes 22A-22 ntransmit and receive data traffic and control signals.

The optical nodes 22A-22 n can be implemented in a variety of ways.Nonexclusive examples include optical line terminals (OLTs), opticalcross connects (OXCs), optical line amplifiers, optical add/dropmultiplexer (OADMs) and/or reconfigurable optical add/drop multiplexers(ROADMs), interconnected by way of intermediate links. OLTs may be usedat either end of a connection or intermediate link. OADM/ROADMs may beused to add, terminate and/or reroute wavelengths or fractions ofwavelengths. Optical nodes are further described in U.S. Pat. No.7,995,921 titled “Banded Semiconductor Optical Amplifiers andWaveblockers”, U.S. Pat. No. 7,394,953 titled “Configurable IntegratedOptical Combiners and Decombiners”, and U.S. Pat. No. 8,223,803(Application Publication Number 20090245289), titled “Programmable TimeDivision Multiplexed Switching,” the entire contents of each of whichare hereby incorporated herein by reference in its entirety.

FIG. 2A illustrates an example of the optical node 22A being a ROADMsite 37 that interconnects optical fiber links 30A, and 30E, and 13.Fiber links 30A, 30E and 13 may include optical fiber pairs, whereineach fiber of the pair carries optical signal groups propagating inopposite directions. As seen in FIG. 2A, for example, optical fiber link30A includes a first optical fiber 30A-1, which carries optical signalstoward optical node 22A, and a second optical fiber 30A-2 that carriesoptical signals output from optical node 22A. Similarly, optical fiberlink 13 may include optical fibers 13-1 and 13-2 carrying optical signalgroups to and from the optical node 22A, respectively. Further, opticalfiber link 30E may include first (30E-1) and second (30E-2) opticalfibers also carrying optical signals from and to optical node 22A,respectively. Additional nodes, not shown in FIG. 2A, may be providedthat supply optical signal groups to and receive optical signal groupsfrom optical node 22A. Such nodes may also have a ROADM having the sameor similar structure as that of optical node 22A.

As further shown in FIG. 2A, receive portion 38-1 and transmit portion38-2 may be provided adjacent the ROADM site 37 to add and drop opticalsignal groups, respectively.

The optical node 22A including transmit (38-2) and receive (38-1)portions will next be described in greater detail with reference toFIGS. 2B and 2C. As shown in FIG. 2A, optical node 22A may include aplurality of wavelength selective switches (WSSs), such as WSSs 39-1 to39-6. Wavelength selective switches are known components that candynamically route, block and/or attenuate all the received opticalsignal groups input from and output to optical fiber links 30A, 13, and30B. In addition to transmitting/receiving optical signal groups fromthese nodes, optical signal groups may also be input from or output totransmit and receive portions 38-2 and 38-1, respectively, in or nearROADM site 37.

As further shown in FIG. 2A, each WSS 39-1 to 39-6 can receive opticalsignal groups and selectively direct such optical signal groups to otherWSSs for output from optical node 22A. For example, WSS 39-6 may receiveoptical signal groups on optical communication path 30A-1 and supplycertain optical signal groups to WSS 39-3, while other are supplied toWSS 39-2. Those supplied to WSS 39-3 may be output to optical node 22Don optical communication path 30E-1, while those supplied to WSS 39-2may be output to another optical node (not shown) on opticalcommunication path 13-2. Also, optical signal groups input to opticalnode 22A on optical communication path 30E-2 may be supplied by WSS 39-4to either WSS 39-5 and on to optical node 22B via optical communicationpath 30A-2 or WSS 39-2 and on to another node (not shown) via opticalcommunication path 13-2. Moreover, WSS 39-1 may selectively directoptical signal groups input to optical node 22A from opticalcommunication path 13-1 to either WSS 39-5 and onto optical node 22B viaoptical communication path 30A-2 or to WSS 39-3 and onto optical node22D via optical communication path 30E-1.

WSSs 39-1, 39-4, and 39-6 may also selectively or controllably supplyoptical signal groups to receive portion 38-1 and optical signal groupsmay be selectively output from transmit portion 38-2 in optical node22A. The optical signal groups output from transmit portion 38-2 may beselectively supplied to one or more of WSSs 39-3, 39-2, and 39-5, foroutput on to optical communication paths 30E-1, 13-2, and 30A-2,respectively.

Transmit and receive portion 38-2/38-1 are shown in greater detail inFIGS. 2B and 2C. Receive portion 38-1 includes optical amplifiers 42-1to 42-3 that receive optical signal groups from WSSs 39-1, 39-4, and39-6, respectively. The optical amplifiers 42-1 to 42-3, may eachinclude a segment of erbium doped fiber, which may be pumped to providegain for the received optical signal groups. The amplified opticalsignal groups may then be supplied to a multi-cast switch (MCS) 43,which controllably directs the received optical signals to one ofreceivers (Rx) 44-1 to 44-3.

The receivers 44-1 to 44-3, may have an input that receives an opticalsignal group and supplies the optical signal group to a demultiplexer,such as arrayed waveguide grating (AWG). The AWG may separate theoptical signals within the received group based on wavelength and supplyeach optical signal to a corresponding one of optical components. Asnoted above, the optical signals may be polarization multiplexed, suchthat a polarization splitter or decombiner may be provided in eachreceiver the separate the TE and TM components, for example, of eachoptical signal. The TE and TM components may then be processedseparately. As further noted above, the TE and TM components may bemodulated in accordance with an m-ary modulation format (m being aninteger greater than or equal to 1), e.g., binary phase shift keying(BPSK), quadrature phase shift keying (QPSK), 8-QAM, 16-QAM or higherdata rate modulation format, such that each is preferably subject tocoherent detection to effectively demodulate and detect the data carriedby each optical signal. Here, optical components may each include knownoptical hybrid circuitry, as well as a local oscillator laser, and theoutputs of optical components may be supplied to respectivephotodetector circuitry (PDs). The optical signals may then be convertedto corresponding electrical signals by PDs, each of which may includeknown balanced detectors. The electrical signals output from PDs arethen provided to processing circuits, each of which includes known clockand data recovery circuitry to demodulate and output data carried by theoptical signals in the optical signal group supplied to the AWG.

It is understood that receivers 44-2 to 44-3 may have the same orsimilar structure as the receiver 44-1 described above.

Returning to FIG. 2C, transmit portion 38-2 will next be described ingreater detail. Transmit portion 38-2 includes a plurality oftransmitters 46-1 to 46-3, each of which supply a corresponding opticalsignal group to a respective one of optical amplifiers 47-1 to 47-3. Thetransmitter 46-1, for example, includes a plurality of lasers, each ofwhich supplies a corresponding unmodulated optical signal having aparticular wavelength to a respective one of optical circuits. Eachoptical circuit may include optical modulators, splitters, polarizationrotators, amplifiers, and other optical components for modulating,amplifying, and/or polarization multiplexing portions of the lightoutput from each laser. Modulated optical signals output from eachoptical circuit are next combined by a known optical multiplexer, suchas an AWG onto an output waveguide as an optical signal group. Each pairof laser and optical circuit may collectively constitute an opticalsource.

As noted above, in one example, the modulated optical signals may bepolarization multiplexed, such that TE and TM components of each opticalsignal are separately modulated and combined. In that case, one or morepolarization beam combiners may be provided in each transmitter tocombine such components. In addition, known optical circuitry may beprovided to modulate the TE and TM components in accordance with anm-ary modulation format, such as BPSK, QPSK, 8-QAM, 16-QAM or higherdata rate modulation format.

It is noted that each optical signal within each optical signal groupdiscussed above may have a wavelength near 1550 nm.

Returning to FIG. 2C, each optical amplifier 47-1 to 47-3 includes acorresponding segment of erbium doped fiber (48-1 to 48-3), which asnoted above, can be pumped to provide gain over a range of wavelengths,including the wavelengths of optical signals in the optical signalgroups output from transmitters 46-1 to 46-3. Transmitters 46-1 to 46-3and optical amplifiers 48-1 to 48-3 may be provided in respectivemodules 49-1 to 49-3. Each of the modules 49-1 to 49-3 may be a linecard, for example.

The amplified optical signal groups may next be supplied to acorresponding one of filters 50-1 to 50-3 and then provided to amulti-cast switch (MCS) 51, which switches the received optical signalgroups to one of amplifiers 52-1 to 52-3, each of which including acorresponding one of erbium-doped fibers 53-1 to 53-3. Each opticalamplifier, in turn, outputs the received optical signal groups, inamplified form, to a corresponding one of WSSs 39-2, 39-3, and 39-5.Thus, MCS 51 may be controlled to output a particular optical signalgroup to a desired WSS, and then onto a desired node. As a result, ofsuch switching, optical node 22A is reconfigurable so that each opticalsignal group can be selectively or controllably output to any desiredoutput, and thus to a desired node.

The optical node 22A also includes a roadm node controller 54communicating with the SDN L0 network controller 24 via the network 26,and an optical channel monitor 55 supplying control information to theroadm node controller 54.

The optical channel monitor 55 includes circuitry to monitor the powerof optical signals on the optical communication paths 13-1, 13-2, 30A-1,30A-2, 30E-1 and 30E-2 to obtain network performance parameters, such asvalid channel detection, center wavelength and an optical signal tonoise ratio. The network performance parameters measured by the opticalchannel monitor 55 are supplied to the roadm node controller 54, andthereafter supplied to the SDN L0 network controller 24. As will bediscussed below, the optical channel monitor 55 is included with atleast two modes, i.e., a steady state mode and a restoration mode thathave different scan rates for measuring the network performanceparameters. In general, the scan rate during the steady state mode isslower than the scan rate during the restoration mode. For example, thescan rate during the steady state mode can be 1 second, and the scanrate during the restoration mode can be 0.1 seconds thereby resulting ina 10 times faster scan rate during the restoration mode. The scan rateduring the restoration mode can be within a range of 2 to 10 timesfaster than the scan rate during the steady state mode.

As illustrated in FIG. 3, the exemplary optical node 22A, may receiveone or more optical control signal 64, from one or more other opticalnodes 22B-22 n in in the optical transport network 20, containinginformation regarding the Operation, Administration, and/or Maintenance(OAM) of optical layers in the optical transport network 20. The opticalcontrol signal 64 may be carried via the Optical Supervisory Channel(OSC) 32, or any suitable optical control channel. The optical layer OAMinformation, such as status and defect information, is mapped tospecific bits in OSC 32. The OAM information communicated for a givendata signal may be based at least in part on the health of the hardwarein the path of the data signal and the health of the optical data pathitself. Methods and systems for transmitting and receiving OAM datawithin the OSC 32 are more fully described in the patent applicationidentified by U.S. Ser. No. 13/452,413, titled “OPTICAL LAYER STATUSEXCHANGE OVER OSC-OAM METHOD FOR ROADM NETWORKS” filed on Apr. 20, 2012.

In general, the optical control signal 64 is terminated at the opticalnode 22A, as illustrated in FIG. 3, where the control module 60 extractsthe optical layer overhead OAM information from the optical controlsignal 64 in the OSC 32. The optical node 22A may notify software 62 inthe optical node 22A and/or may notify other optical nodes 22B-22 n inthe optical transport network 20 of the status of the optical layer, asindicated by the overhead information. In one embodiment, the opticalnode 22A inspects the optical control signal 64 for stable values beforenotifying the software 62 of the status of the optical layer. Thefiltering for stable values may be done in hardware, in which case, theassociation of filtering characteristics to fields may be fixed in thehardware code, for example, in a FPGA's code. Also, if granularnotifications (interrupts) are provided to the software 62, theassociation of fields to interrupt bits may be fixed in the hardwarecode.

Additionally, the optical node 22A may write, with the software or withhardware, Operation, Administration, and/or Maintenance (OAM)information of the optical layers in the optical transport network 20into overhead of the optical control signal 64 to be transmitted fromthe optical node 22A via the OSC 32. This information may include, forexample, equipment status, incoming signal status, and/or connectivityinformation. Of course, the information may include any OAM information.The optical node 22A may then initiate, with the software, transmissionof the optical control signal 64 via the Optical Supervisory Channel(OSC) 32, or any suitable optical channel.

FIG. 4 is a diagram of example components of the SDN L0 networkcontroller 24. Of course, the SDN L0 network controller 24 componentsmay be distributed into multiple devices, but are preferably separatefrom any of the nodes 22A-22 n.

SDN L0 network controller 24 may include a bus 100, a processor 102, amemory 104, an input component 106, an output component 108, and acommunication interface 110. In some implementations, SDN L0 networkcontroller 24 may include additional components, fewer components,different components, or differently arranged components than thoseillustrated in FIG. 4.

Bus 100 may include a path that permits communication among thecomponents of SDN L0 network controller 24. Processor 102 may include aprocessor, a microprocessor, and/or any processing logic (e.g., afield-programmable gate array (“FPGA”), an application-specificintegrated circuit (“ASIC”), etc.) that may interpret and executeinstructions. Memory 104 may include a random access memory (“RAM”), aread only memory (“ROM”), and/or any type of dynamic or static storagedevice (e.g., a flash, magnetic, or optical memory) that may storeinformation and/or instructions for use by processor 102.

Input component 106 may include any mechanism that permits a user toinput information via a device 112 (e.g., a keyboard, a keypad, a mouse,a button, a switch, etc.). Output component 108 may include anymechanism that outputs information (e.g., a display, a speaker, one ormore light-emitting diodes (“LEDs”), etc.). Communication interface 110may include any transceiver-like mechanism, such as a transceiver and/ora separate receiver and transmitter that enables the SDN L0 networkcontroller 24 to communicate with other devices and/or systems, such asthe nodes 22A-22 n via the network 26. The network 26 can be implementedas a wired connection, a wireless connection, or a combination of wiredand wireless connections.

SDN L0 network controller 24 may perform various operations describedherein. SDN L0 network controller 24 may perform these operations inresponse to processor 102 executing software instructions contained in anon-transitory computer-readable medium, such as memory 104. Acomputer-readable medium may be defined as a non-transitory memorydevice. A memory device may include space within a single storage deviceor space spread across multiple storage devices.

Software instructions may be read into memory 104 from anothercomputer-readable medium or from another device via communicationinterface 110. Software instructions stored in memory 104 may causeprocessor 102 to perform processes that are described herein.Additionally, or alternatively, hardwired circuitry may be used in placeof or in combination with software instructions to implement processesdescribed herein. Thus, implementations described herein are not limitedto any specific combination of hardware circuitry and software.

SDN L0 network controller 24 may include a restoration manager 120 and arestoration policy handler 122. Each of functional components 120 and122 may be implemented using one or more components of the SDN L0network controller 24. The restoration policy handler 122 may includemultiple different restoration policies as options, such as fullsequential vs. full parallel settings. A full sequential restorationpolicy brings up the links one by one in a serial manner, and fullparallel restoration policy brings up the links in a parallel manner asdisclosed herein. Selection of a particular restoration policy to beperformed in restoring a restoration path can be selected in advance ofa failure to a primary path. Restoration aggressiveness can be chosen bythe SDN L0 network controller 24 or by a user (e.g., using the device112). The restoration manager 120 is configured to monitor all or asubset of links within the optical transport network 20, obtain networkperformance information discussed above on a random or periodic basis(e.g., every 10 seconds) during operation of the primary path 34, andprovide information to the Nodes 22A-22 n in parallel to restore therestoration path as described herein. The restoration manager 120 mayalso be configured to determine restoration policy (e.g.,fast/aggressive vs. slow/safe, i.e. parallel vs. sequential), monitoringthe links 30 a-m for faults. Selecting restoration paths frompre-selected paths or trigger Path Computation Engine (in the SDN L0network controller 24) to calculate a new path for the service beingaffected by a fault. The restoration manager 120 may include a networktopology database stored in the memory 104. The network topologydatabase includes information indicative of the entire network topologyof the optical transport network 20. The restoration manager 120 updatesthe network topology database with information indicative of anytopology changes, as well as any updates to the network performanceinformation. Because the SDN L0 network controller 24 is separate fromthe nodes 22A-22 n, and communicates with the nodes 22A-22 n inparallel, the SDN L0 network controller 24 can listen to (receive anynetwork performance information updates) and control all of the nodes22A-22 n in parallel.

In general, upon failure of the primary path 34, the SDN L0 networkcontroller 24 restores the restoration path 36 as follows. First, asindicated by a block 130, the SDN L0 Network Controller 24 detects afailure of the primary path 34, and then determines which communicationlink 30A or 30B has failed. This can be accomplished by analyzing faultmetrics (such as back trace faults) and listening to/monitoring the headend node 22A, the intermediate node 22B and the tail end node 22C inparallel. Once the location of the failure is known, the SDN L0 networkcontroller 24 branches to a block 132 and calculates a L0 restore pathfrom the known network topology information (or the SDN L0 networkcontroller 24 can select from a pre-calculated list based onpreference). Then, as shown in block 134, the SDN L0 network controller24 sends signals, in parallel, to each of the nodes 22A-22 n in therestore path to determine whether the restore path is available. In thisstep, the SDN L0 network controller 24 is checking to see if any faultexists in the restore path, and/or for wavelength availability. If therestore path is unavailable, then the SDN L0 network controller 24branches back to the block 132 to select another restore path. If therestore path is available, the SDN L0 network controller 24 branches tothe block 136. In this block, the SDN L0 network controller 24 enablesthe restore path by controlling each of the nodes 22A-22 n in a parallelfashion, and then determines and manages the power of the restore pathfrom the head end node 22A to the tail end node 22C in a serial mannerbeginning with the head end node 22A.

Turning now to FIG. 6, shown therein is the exemplary optical transportnetwork 20 of FIG. 1, in which a failure, designated by “X”, hasoccurred in the primary path 34. In this example, the failure “X” is thefailure of a uni-directional fiber 70 in communication link 30 betweenoptical node 22A and optical node 22B. Each node 22A-22 n is capable ofdetecting failures and providing status updates to the SDN L0 networkcontroller 24. The optical nodes 22A, 22B, and 22C are also monitoringthe data traffic in the primary path 34 and/or restoration path 36, suchas with the optical channel monitor 55. Node 22B detects uni-directionalfailure “X” and provides status information to the SDN L0 networkcontroller 24 via the network 26 indicative of the location of thefailure “X”.

Upon detection of the location of the failure “X” in primary path 34,the SDN L0 network controller 24 signals the headend node 22A and thetail end node 22C, in a parallel fashion, to switch to the restore pathas the restoration path 36 as the provider of the data traffic, usingswitches 58.

FIG. 7 is a flow diagram of an exemplary protection process 200 forimplementing the block 136 of FIG. 5 in accordance with the presentdisclosure. In a block 202, the restoration manager 120 of the SDN L0Network Controller 24 calculates first power adjustment parametersconfigured to provision each of the nodes 22A, 22D, 22E and 22C in therestoration path 36. In one embodiment, each of the nodes 22A-22 n inthe restoration path includes a Reconfigurable Optical Add-Drop Module(ROADM). In this embodiment, the restoration manager 120 checks to seeif the optical channel monitor 55 within the nodes 22A, 22D, 22E and 22Cin the restore path is in the steady state mode. The restoration manager120 accesses the network topology database stored in the memory 104, toobtain current network performance information, and then calculates thefirst power adjustment parameters using the network performanceinformation. For example, provisioning gains, such as optical amplifiergains, can be calculated during an initial link design phase using alink design tool. In some embodiments, a user inputs the link topology,fiber loss/type information and requested services as input to the linkdesign tool. The link design tool computes the required cards to be usedin the optical nodes 22A, 22D, 22D and 22C, such as amplifiers, ROADMsand line modules. The link design tool also calculates the launch powerinto the fiber. Based on the resulting amp type and the calculatedlaunch power, the link design tool can determine the default/initialgain set points for each amplifier. This can be used as the amplifiergain initially, i.e. during provisioning of the amplifiers for the firsttime. Based on estimates of the optical amplifier gains and loading, anestimated line spread at the tail end node 22C can be calculated. Iftraffic exists on the restoration path 36, then real-time measured linespread data at the tail end node 22C can be retrieved from the networkperformance data in the network topology database. In either case, themeasured line spread or the estimated line spread and degree insertionlosses from a ROADM Node Controller which interfaces with the SDN L0network controller 24, for example, pre-stored for each establishedconnection, e.g., the optical cross connect in the wavelength selectiveswitch(es) is used to estimate passband attenuation at each wavelengthselective switch cross connect at each of the nodes 22A, 22D, 22E and22C in the path of the restoration path 36. The data in the networktopology database is preferably captured from the nodes 22A, 22D, 22Eand 22C when the optical channel monitor 69 within these nodes 22A, 22D,22E and 22C is in the steady state mode.

In a block 204, the restoration manager 120 transmits a message to thehead end node 22A of the restoration path to cause the head end node 22Ato reduce a source of transmitter launch optical power on therestoration path to a safe value, e.g., −1 dB. Then, in a block 206, therestoration manager 120 transmits messages, in parallel, to the head endnode 22A, the tail end node 22E and at least one intermediate node 22Dand 22E to (1) provision all cross connects within the WSS on therestoration path with estimated passbands, and (2) set the power of alloptical amplifiers in the restoration path or attenuation offsets inaccordance with the estimated provisioning gains. In a block 208, therestoration manager 120 sends a message to the ROADM node controller 54of the head end node 22A, and any other node 22 providing optical powerinto the restoration path, to supply optical power into the restorationpath. The restoration manager 120 also sends a message to the head endnode 22A, the tail end node 22C and the intermediate nodes 22D and 22Eto cause the head end node 22A, the tail end node 22C and theintermediate nodes 22D and 22E to switch the optical channel monitors 55to the restoration mode to enhance the scan rate of the optical channelmonitors 55. Then, as power is being supplied into the restoration path,the restoration manager 120 monitors each of the nodes 22A, 22D, 22E and22C and then supplies messages in a serial sequence to the nodes 22A,22D, 22E and 22C to fix any attenuation/gain set point with availablepower in real time. Optionally, the restoration manager 120 can thensend a message to the head end node 22A, and any other node 22 providingoptical power into the restoration path, to adjust the launch power to atarget power as indicated by block 210. Once the target power has beenreached, the restoration manager 120 sends a message to the head endnode 22A, the tail end node 22C and the intermediate nodes 22D and 22Eto cause the head end node 22A, the tail end node 22C and theintermediate nodes 22D and 22E to switch the optical channel monitors 69to the steady state mode to reduce the scan rate of the optical channelmonitors 69.

FIG. 8 is a diagram of example components of a L0 power controller 220.It should be noted that the L0 power controller 220 components may bedistributed into multiple devices, but are preferably separate from anyof the nodes 22 a-22 n.

L0 power controller 220 may include a bus 222, a processor 224, a memory226, an input component 228, an output component 230, a communicationinterface 232, a device 234, an orchestrating module (PCO) 236, amaintenance module (PCM) 238, an analytic module (PCA) 240, a linkdesign module (LDM) 242, and a L0 dependency matrix traffic engineeringdatabase (DMTED) 244. In some implementations, L0 power controller 220may include additional components, fewer components, differentcomponents, or differently arranged components than those illustrated inFIG. 8.

Bus 222 may include a path that permits communication among thecomponents of L0 power controller 220. Processor 224 may include aprocessor, a microprocessor, and/or any processing logic (e.g., afield-programmable gate array (“FPGA”), an application-specificintegrated circuit (“ASIC”), etc.) that may interpret and executeinstructions. Memory 226 may include a random access memory (“RAM”), aread only memory (“ROM”), and/or any type of dynamic or static storagedevice (e.g., a flash, magnetic, or optical memory) that may storeinformation and/or instructions for use by processor 224.

Input component 230 may include any mechanism that permits a user toinput information via device 234 (e.g., a keyboard, a keypad, a mouse, abutton, a switch, etc.). Output component 230 may include any mechanismthat outputs information (e.g., a display, a speaker, one or morelight-emitting diodes (“LEDs”), etc.). Communication interface 232 mayinclude any transceiver-like mechanism, such as a transceiver and/or aseparate receiver and transmitter that enables the L0 power controller220 to communicate with other devices and/or systems, such as the nodes22A-22 n via the transport network 20. The transport network 20 can beimplemented as a wired connection, a wireless connection, or acombination of wired and wireless connections.

L0 power controller 220 may perform various operations described herein.L0 power controller 220 may perform these operations in response toprocessor 224 executing software instructions contained in anon-transitory computer-readable medium, such as memory 226. Acomputer-readable medium may be defined as a non-transitory memorydevice. A memory device may include space within a single storage deviceor space spread across multiple storage devices.

Software instructions may be read into memory 226 from anothercomputer-readable medium or from another device via communicationinterface 232. Software instructions stored in memory 226 may causeprocessor 224 to perform processes that are described herein.Additionally, or alternatively, hardwired circuitry may be used in placeof or in combination with software instructions to implement processesdescribed herein. Thus, implementations described herein are not limitedto any specific combination of hardware circuitry and software.

The PCO 236 orchestrates operations associated with L0 servicesincluding, for instance, service creation/deletion/modification eitherduring service activation or service restoration. The PCO 236 supportspower control models that are relevant to different operation modelsincluding, for instance, OpenConfig, OpenROADM and Infinera OLS model(OpenOLS).

The PCM 238 causes the L0 power controller 220 to perform periodicmaintenance over a L0 domain of the transport network 20 includingorchestration of the carrier power level, control of transmission linecontroller processes associated with an optical transmission line, andmonitoring all control parameters (e.g., gain, attenuation, and tilttargets). The periodic maintenance is designed to catch deviations fromtarget power levels within the transport network 20 due to exemplaryfactors such as temperature, aging, physical disturbances, etc. in thetransport network 20. The periodic maintenance can be run asynchronouslyon the entire transport network 20.

Components such as, for instance, in-line amplifiers (elements 322 a and322 b in FIG. 11), ROADM nodes (elements 320 a, 320 b, and 320 c in FIG.11), or each interface of the ROADM nodes (e.g., degrees elements 262and 264 in FIG. 10 and/or optical add/drop interfaces element 266 inFIG. 10) of the transport network 20 may be target points for theperiodic maintenance. Each of the target points may be provided with atarget power and a monitoring tool (not shown), e.g., a photo-diode, anoptical power monitor (OPM), and/or optical channel monitor (OCM). Thetarget power, or power spectrum for each optical channel or service isreceived with the service definition. The target power may be stored,for instance, in the memory 226 associated with the target point.

The PCM 238 communicates with the monitoring tools of the target pointsthrough the communication interface 232 using streaming services andreceives data corresponding to the operation of the target point. ThePCM 238 compares the operational data of the target point to the targetpower associated with that target point and determines if there is aconvergence. If there is a convergence, the L0 power controller 220traces the affected service or services using a dependency matrix thatwill be described further herein until the L0 power controller 220localizes the change. Once the change is localized, the L0 powercontroller 220 begins executing power controls starting from thelocation of the change.

The PCA 240 is configured to analyze network performance to derivepatterns of degradation. Based on the patterns of degradation, the L0power controller 220 performs link optimization.

The LDM 242 calculates optimal signal launch powers for each fiber spanin the network using different constraints such as, for instance,performance, cost, margin, etc. Based on link design, the LDM 242calculates an aggregate target power where multiple services arecombined. For instance, when optical channels are multiplexed in a ROADMnode, LDM 242 calculates the aggregate target power of the multiplexedoptical channels.

The DM TED 244 is configured to store network control status anddependency information. The dependency information stored in the DM TED244 includes dependencies between the individual carrier(s), the ROADMnode, and the optical transmission line between ROADM nodes. When awavelength service (i.e. a channel) is added to or removed from thetransport network 20, an entry corresponding to the wavelength serviceis added or removed from the DM TED 244.

FIG. 9 is a block diagram illustrating how the L0 power controller 220interacts with components that may be present on the transport network20. The L0 power controller 220 receives L0 service definitions 246 fromSDN L0 network controller 24.

The L0 power controller 220 receives topology information 248representative of the mapping between the network view and the modelpresent in an OLS controller 306 a (FIG. 11).

L0 resource management 250 provides the L0 power controller 220 withinformation associated with network resources such as ROADM nodes 320a-320 c (FIG. 11), degree nodes 262 and 264 (FIG. 10), SRG A/D node 266(FIG. 10), links, spans, and in-line amplifiers 322 a and 322 b (FIG.11), for instance.

Device controller 252 provides the L0 power controller 220 withinformation indicative of a mapping between a data model present in theL0 power controller 220 and a data model present in OLS controllers 306a-306 c (FIG. 11).

FIG. 10 illustrates an example of an optical node 260 which is a ROADMnode that has been disaggregated into a first degree node 262, a seconddegree node 264, and a shared risk group add/drop node (SRG A/D node)266 that interconnect optical fiber links 267 a, 267 b, and 267 c.

The first degree node 262, second degree node 264, and SRG A/D node 266are provided with degree multiple optical dense wavelength divisionmultiplexing interface (DMW) 269 a-269 f that interconnect the firstdegree node 262, second degree node 264, and SRG A/D node 266 throughoptical spectrum connections 270 a-270 c. It should be noted that insome embodiments, DMW 269 a-269 f may be used to interconnect directlywith terminal optics (not shown).

The first degree node 262 and the second degree node 264 are providedwith at least one multiple optical dense wavelength divisionmultiplexing interface (MW) 272 a and 272 b, respectively, whichinterface with fiber links 267 a and 267 b, respectively.

The SRG A/D node 266 is provided with at least one add/drop multipleoptical dense wavelength division multiplexing interface (ADW) 274 a-274c that interface with optical fiber links such as optical fiber link 267c to connect the SRG A/D node 266 with terminal optics.

FIG. 11 illustrates an example SDN architecture 298 where a centralizedSDN L0 network controller 300 manages L0 service between terminal optics310 and 312 over a reconfigurable optical network 313. The transportnetwork 20 is an example of the reconfigurable optical network 313.

The SDN L0 network controller 300 communicates with L0 power controller302 through an open interface 304 to exchange information about L0service definitions that include, for instance, XPDR information andROADM optical spectrum connection.

The L0 power controller 302 communicates with the OLS controllers 306a-306 c to implement the services into the different components thatdefine the reconfigurable optical network 313 through open interfaces308 a-308 c.

The L0 power controller 302 communicates with the terminal optics 310and 312 to exchange information regarding the power control of theterminal optics 310 and 312 through open interfaces 314 and 316,respectively.

In the illustrated embodiment, the OLS controllers 306 a-306 c manageROADM node 320 a-320 c and ILA 322 a-322 b components through openinterfaces 324 a-324 f and 326 a-326 b, respectively.

FIG. 12 illustrates another example SDN architecture 348 where a SDN L0network controller 350 manages L0 service between terminal optics 360and 362 over a reconfigurable optical network 364.

In SDN architecture 348, SDN L0 network controller 350 is responsiblefor configuration and monitoring of terminal optics 360 and 362 toinclude any power control information such as the optical power targetof transmitters.

SDN L0 network controller 350 communicates with a L0 power controller352 through an open interface 354 to exchange information about the L0service definitions. L0 power controller 352 is responsible formonitoring and controlling network components between the terminaloptics 360 and 362.

FIG. 13 illustrates an example multi-domain SDN architecture 400 where aSDN L0 network orchestrator 402 manages multiple SDN L0 networkcontrollers 404 and 406 to orchestrate the operation of a multi-domainoptical network 408 beginning with terminal optic 410 and ending atterminal optic 412.

For each SDN L0 network controller 404 and 406, an L0 power controller414 and 416 exists to manage the multi-domain optical network 408 tocontrol the optical power. Control information is exchanged between L0power controllers 414 and 416 over external domain L0 power controlinterface 420.

An external network to network interface (ENNI) 418 opticallyinterconnects each domain of the multi-domain optical network 408. TheENNI 418 information is known by the L0 power controllers 414 and 416that participate in this interconnection.

It should be noted that SDN L0 network controllers 300, 350, 404 and 406and SDN L0 network orchestrator 402 may be constructed substantially thesame as SDN L0 network controller 24 and L0 power controllers 302, 352,414, and 416 may be constructed substantially the same as L0 powercontroller 220.

As illustrated in FIG. 14A, the ENNI 418 may be located betweendifferent components of an open line system. For instance, the ENNI 418may be connected between a first degree 450 and a second degree 452 of adisaggregated ROADM 454 via DMW interfaces (not shown).

As illustrated in FIG. 14B, the ENNI 418 may be connected between adegree 460 and an adjacent ILA 462.

As illustrated in FIG. 14C, the ENNI 418 may be connected between afirst ILA 470 and a second ILA 472.

FIG. 15 illustrates an optical network segment 490 illustrating possiblepower spectral density (PSD) measuring points 492 a-492 d in the opticalnetwork segment 490.

FIG. 16 is a block diagram illustrating a portion of a SDN architecture500 having a L0 power controller 502 (similar to L0 power controller220) communicating with a first OLS controller 504 and a second OLScontroller 506 over open interface 508 and open interface 510,respectively.

First OLS controller 504 is provided with a first ROADM node controller(RNC) 512, a second RNC 514, and a transmission line controller (TLC)516. The first and second RNC 512 and 514 and the TLC 516 communicatewith elements of an optical network segment 517 over open interfaces 518a-518 d. In particular, the first RNC 512 communicates with SRG A/D node520 of a disaggregated ROADM node 522 over open interface 518 a. Thesecond RNC 514 communicates with degree node 524 over open interface 518b. The TLC 516 communicates with a first ILA 526 over open interface 518c. The TLC 516 communicates with a second ILA 528 over open interface518 d.

Second OLS controller 506 is provided with a third RNC 530 and a fourthRNC 532. The third and fourth RNC 530 and 532 communicate with elementsof the optical network segment 517 over open interfaces 534 a-534 b. Inparticular, the third RNC 530 communicates with degree node 536 of adisaggregated ROADM node 538 over open interface 534 a. The fourth RNC532 communicates with degree node 540 over open interface 34 b.

It should be noted that a single RNC may provide power control of allelements of a ROADM node instead of one RNC for each element asillustrated in FIG. 16. By way of non-limiting illustration, in FIG. 17,an RNC 580 provides power control of all elements of a ROADM node 582.In such an embodiment, L0 power controller 552 communicates with OLScontroller 554 over open interface 556. OLS controller communicates withthe RNC 580 and RNC 580 communicates with a first degree 558 and asecond degree 560 of the ROADM node 582 over open interface 562.

FIG. 18 illustrates a multi-domain optical network 600 having a firstdomain 602 and a second domain 604 interconnected through an ENNIinterface 606 illustrated as an express connection between a firstdegree 608 and a second degree 610 of a ROADM node 612. In theillustrated embodiment, a first L0 power controller 614 provides powercontrol for network elements of the first domain 602 and a second L0power controller 616 provides power control for network elements of thesecond domain 604. Control information is exchanged between the first L0power controller 614 and the second L0 power controller 616 over anexternal domain L0 power controller interface 618.

To communicate a state of each L0 power controller 614 and 616 over theexternal domain L0 power controller interface 618, the first L0 powercontroller 614 and the second L0 power controller 616 use acommunication protocol such as Distributed Power Control Protocol(DPCP), for instance. This way, the first and second L0 powercontrollers 614 and 616 are able to orchestrate and maintain amulti-domain optical network.

FIG. 19 illustrates an optical transmission line 650 between a firstdegree node 652 and a second degree node 654. Generally, opticaltransmission line 650 are provided with one or more in-line opticalamplifiers (ILAs) to boost signal power and extend transmissiondistance. In some embodiments, some of the ILAs may be provided withspectrum equalizers to correct for the line spread or the gain tilt ofthe optical amplifiers. In the illustrated embodiment, the transmissionline 650 is provided with a first ILA 656, a second ILA 658, and a thirdILA 660.

The process of controlling the power within optical transmission line650 is governed by a transmission line controller (TLC) 662. TLC 662monitors the input and output power of each control loop in the opticaltransmission line 650 (such as gain controls on an erbium doped fiberamplifier, for instance) and correct the amplifier gain in relation tothe ingress optical power and to an estimator of the total output powerthat should be present at the output of the ILA.

The TLC 662 interfaces with an L0 power controller 220 (FIG. 8) asdescribed herein, however, it is an abstraction layer for the lowerlevel controls—such as ILA control loops. Therefore, TLC 662 may governmultiple control loops and may implement the orchestration of theexecution of those control loops within itself.

The L0 power controller 220 ensures target powers calculated by the LDM242 (FIG. 8) are achieved in an optical network. LDM 242 calculates theoptimal signal launch powers for each fiber span 664 a-664 d in theoptical transmission line 650. The optimization can be done withdifferent constraints (e.g., performance, cost, margin, etc.). In orderto achieve the design objectives, the L0 power controller 220 performsperiodical maintenance checks to catch deviations from the powertargets. The deviations can be due to several reasons including, but notlimited to, temperature, aging, physical disturbances, etc.

Each element in the optical network (e.g., first degree 652, seconddegree 654, first ILA 656, second ILA 658, and third ILA 660) is atarget point. Each target point has a target power and a monitoring tool(Photo-diode and/or OCM). The L0 power controller 220 runs periodicaudits at the targeting points through streaming services to catchdeviations from the power targets. Each element in the optical networkincludes an API that support streaming of the monitored parameters. Thestreaming services can use a communication mechanism like IP overEthernet over the OSC or DCN channel that is normally present in theoptical network. Periodic audits can be run asynchronously on the entirenetwork

FIG. 20 illustrates an exemplary ROADM network 700 having a plurality ofROADM nodes 702 a-702 e interconnected by optical transmission lines 704a-704 e. A first optical transmitter 706, a second optical transmitter708, and a third optical transmitter 710 provide optical carrier signals712 a-712 c which are carried over the ROADM network 700 to a firstoptical receiver 714, a second optical receiver 716, and a third opticalreceiver 718, respectively. The optical carrier signals 712 a-712 c aretransmitted through various ROADM nodes 702 a-702 e interconnected byoptical transmission lines 704 a-704 e of the ROADM network 700. When anoptical carrier 712 a-712 c requires the use of an optical transmissionline 704 a-704 e or a ROADM node 702 a-702 e, the optical carrier issaid to be dependent on that network element. For instance, opticalcarrier 712 a is transmitted through ROADM node 702 a, opticaltransmission line 704 a, ROADM node 702 b, optical transmission line 704b, and ROADM node 702 c. Consequently, optical carrier 712 a isdependent on ROADM node 702 a, optical transmission line 704 a, ROADMnode 702 b, optical transmission line 704 b, and ROADM node 702 c.

A L0 power controller such as L0 power controller 220 described above isconfigured to gather and store dependency information in the DM TED 244.The DM TED 244 is configured to store network control status anddependency information. The dependency information stored in the DM TED244 includes dependencies between the individual optical carrier(s), theROADM node, and the optical transmission line between ROADM nodes. Whena wavelength service (i.e. an optical channel) is added to or removedfrom the ROADM network 700, an entry corresponding to the opticalchannel is added or removed from the DM TED 244.

A power control process in the L0 power controller 220 uses abacktracking process to resolve optical power issues that happen in theROADM network 700. The power control process is triggered by thedetection of deviations in optical channel power at ROADM degreelocations or deviations in the total output or input power present attarget points (e.g., ILAs) in optical transmission lines.

The L0 power controller 220 runs periodic maintenance cycles or auditsto monitor all control parameters (e.g., gain, attenuation, tilttargets) and compare the control parameters to targets. When a deviationis detected for an optical channel, the L0 power controller 220backtracks the path of the optical channel using the DM TED 244 tovalidate the quality of the ROADM network 700. When a starting point forthe deviation is found, the L0 power controller 220 starts power repairsfrom that point. When the start point of a deviation is an ILA, thesystem backtracks all affected optical channels and starts to repairfrom a point where optical channels can be re-routed (e.g., a degreenode or an SRG A/D node).

FIG. 21 illustrates a block diagram of an exemplary control loop statemachine 750 in accordance with the present disclosure. Each target pointin an optical network has a control loop. Each control loop will bemaintained and monitored by one control loop state machine 750 whichwill not run on the hardware itself. Instead, the control loop statemachine 750 will run in a higher, abstracted layer. For instance, thecontrol loop for SRG A/D node 520 in FIG. 16 would run in RNC 512.

The target point to which the control loop state machine 750 is assignedis called the device under control (DUC). DUC set values are definedconsistently in sign in terms of gain/attenuation (i.e., negative ifdevice is providing attenuation and positive if device is providinggain). DUCs are provided with monitoring tools (PM) such as aphoto-diode and/or OCM which monitor power at input, output, or both.Monitoring tools might be PD (full band) or OPM (full band or per-sch).The DUC will have a corresponding band for controls.

All available monitoring tools will be monitored for stability bycomparing target power vs. current values. If a DUC is found to beunstable, e.g., the current power and the target power show aconvergence, the corresponding control loop will request a run.

For the sake of illustration, the control loop state machine 750 will bedescribed herein as monitoring and controlling a WSS. However, it shouldbe noted that certain internal actions within the states described mightbe different depending on the loop type and control mode. Therefore, theactions and/or power levels described are provided for illustrationpurposes only and should not be considered as limiting.

The control loop state machine 750 is provided with a running superstate 756 and an idle super state 758. By default, i.e. once aconnection has been created but control mode is off, the control loopstate machine 750 will be operating in idle super state 758 and set to aBLOCKED state. When an UNBLOCK command is received, the control loopstate machine 750 moves to a READY state. When the control loop statemachine 750 receives the command to enable the control loop, the controlloop state machine 750 moves to the STANDBY state. In the STANDBY state,the control loop state machine 750 continuously monitors theinput/output monitoring tools and target vs. current values. If adeviation is found, the control loop state machine 750 sends anATTENTION RQST indicating the control loop needs attention. Aftersending the ATTENTION RQST, the control loop state machine 750 moves toa PENDING state waiting for instructions.

When the control loop state machine 750 receives a RUN or a RUN with NEWDATA command, the control loop state machine 750 moves to the INITIALIZEstate in the running super state 756. In the INITIALIZE state, thecontrol loop state machine 750 verifies the target device is reachable,verifies OLOS at the input monitoring tool is cleared (if service isalready up), verifies the input parameters for the Control Loop isrefreshed after the previous control loop, and runs an instability checkon monitoring tools based on historic samples (again, not that theremight be different requirements for TLC loops and other loops). IfPROVISION and RUN is received, the control loop state machine 750configures the target device.

If the control loop state machine 750 receives an ABORT command, theinitialization fails, or a predetermined time is reached beforeinitialization is complete, the control loop state machine 750 returnsto the STANDBY state.

Upon completion of initialization, the control loop state machine 750moves to the CALCULATION state were the control loop state machine 750runs calculations based on control loop type.

If the calculations take too long, i.e., a predetermined time is reachedbefore the calculations are completed, the control loop state machine750 moves to the STANDBY state and begins monitoring again. Further, ifthe calculations are run and the control loop state machine 750determines that no adjustments are needed, the control loop statemachine 750 moves to the STANDBY state and begins monitoring again.

If the control loop state machine 750 determines that adjustments areneeded, the control loop state machine 750 moves to the ADJUSTING stateand runs a pre-check to determine if the control loop is stable. If thecontrol loop is stable, the control loop state machine 750 startsadjusting the DUC set point, following any ramping if needed.

Once adjustments are completed, an ABORT command is received, theadjustment reaches a predetermined time before completing theadjustment, upon full converge, or upon partial converge/clamping, thecontrol loop state machine 750 moves to the STANDBY state.

It should be noted that in some embodiments the states, commands, andmessages are the same across all types of control loops making anycontrol loop able to interact with any other control loop.

Referring now to FIGS. 21 and 22, the control loop state machine 750intakes a set of input parameters, runs internal actions depending onthe type of control loop and/or control mode, and outputs a set ofparameters. Input parameters may be input parameters from manager (whichcome from a power control manager 780) or input parameters as calculatedat previous target point (which may be L0 power controller, the samedegree, another degree, TLC, ILA, or sub-ILA). For example, inputparameters as calculated at previous target point may be communicatedfrom a state machine associated with another degree node whichcommunicates the calculated input parameters to the control loop statemachine 750.

Output parameters may be communicated to L0 power controller, the samedegree, another degree, TLC, ILA, or sub-ILA. For example, the outputparameters may be communicated to a lower level control loop, the nexttarget point, or a power controller (e.g., L0 power controller or SDNnetwork controller).

In some embodiments, all control loops take the same set of powercontrol parameters as input and they provide the same set of parametersas output. This standard interface allows any control loop to interfacewith any other control loop or power controller. Example inputparameters (elements 752 a-752 c) and output parameters (elements 754a-754 d) can be seen in FIG. 21.

Examples of different types of control loops include:

Open Loop (ILA EDFAs, FRM Demux Control Loop (DMCL) in which DUC setpoint (new)=output target (CALC)−input PM

Closed loop (FRM Mux Control Loop (MCL) calculations) in which DUC setpoint (new)=DUC set point (current)+(output target−output PM)

Closed Loop on DUC set Point (Fixed Attenuation on Line Out VOA) inwhich DUC Set Point (New)=DUC Set Point (Current)+(DUC Set Point(Target)−(Output PM−Input PM))

FIG. 23 illustrates an exemplary ROADM node controller power controlstate machine (RNC PCSM) 800. RNC PCSM 800 is a super-state machine andacts as the local orchestrator and message handler within an RNC 802.Control loops run within the RNC PCSM 800 may be run in series or inparallel. For instance, the mux control loops (MCL) 804 a-804 n areshown being executed in parallel.

In an exemplary flow, upon detection of a deviation in MCL 804 a, forinstance, MCL 804 a will ask for attention from RNC PCSM 800. RNC PCSM800 will then ask for attention from L0 power controller 808. L0 powercontroller 808 orchestrates control loop execution in the network.Hence, when it is the RNC's 802 turn, L0 power controller 808 will senda RUN command to RNC PCSM 800. Then RNC PCSM 800 will send a RUN commandto MCL 804 a internally.

FIG. 24 illustrates an exemplary transmission line controller powercontrol state machine (TLC PCSM) 850 running in a transmission linecontroller (TLC) 852. The TLC PCSM 850 interfaces with L0 powercontroller 854 and acts as the local orchestrator and message handler inthe TLC 852.

In the illustrated example, TLC 852 is connected to a first ILA (notshown) and a second ILA (not shown). For the sake of illustration, thefirst ILA and the second ILA each are provided with a pre-amp (PA) and abooster amp (BA).

TLC PCSM 850 has a first super-state 856 and a second super-state 858.The first super-state 856 is provided with a first ILA PCSM 860, a firstILA PA control loop 862, and a first ILA BA control loop 864.

The second super-state 858 is provided with a second ILA PCSM 866, asecond ILA PA control loop 868, and a second ILA BA control loop 870.

A state of the first super-state 856 and the second super-state 866indicate a status of aggregate states of the underlying control loops ofthe first ILA and the second ILA, respectively. The state of the TLCPCSM 850 indicate a status of aggregate states of the underlying PCSMstates (the first super-state 856 and the second super-state 866).Hence, each level is abstracted by a layer higher above, whichinterfaces with a higher level controller. This higher level controllercan be another layer of abstraction or the L0 power controller 854.

The TLC PCSM 850, first super-state 856, second super-state 858, firstILA PCSM 860, first ILA PA control loop 862, first ILA BA control loop864, second ILA PCSM 866, second ILA PA control loop 868, and second ILABA control loop 870 communicate through internal data.

FIG. 25 is a block diagram illustrating an example SDN architecture 900and ROADM optical network 902. The optical power flow through nodes,amplifiers, and optical fibers of the ROADM optical network 902 create asequential downstream dependency, i.e., a change made/observed at atarget point (e.g. node or amplifier) will also be observed on alldownstream target points. Hence, the dependency is traced and thecontrol loops that affect the input and output powers of other controlloops are handled depending upon the dependency. L0 power controller 904keeps a graphical map 906 of the ROADM optical network 902 and activelytracks the source and destination of each optical channel along with theoptical path (nodes) traversed by the optical channel. This is called adependency matrix for the ROADM optical network 902. This allows L0power controller to monitor and control an overall state of each controlloop.

A hierarchy of control loops is determined based on the dependencymatrix. This hierarchy determines the sequence of execution of controlloops following the optical signal flow. In certain cases, the hierarchyof control loops includes grouped or nested control loops that may berun in parallel because they do not have direct dependence. Forinstance, in the exemplary ROADM optical network 902 illustrated in FIG.25, each optical channel 910 a-910 c may be controlled independently andin parallel in first power control loops 912 a-912 c because none of theoptical channels 910 a-910 c directly depend from each other. Firstcontrol loops 912 a-912 c are maintained and controlled by the L0 powercontroller 904 through communication link 914.

L0 power controller 904 communicates with a first OLS controller 916through the communication link 918. Once all three first control loops912 a-912 c have completed, L0 power controller 904 will send a runcommand to a RNC PCSM 920 running in a first RNC 919. The RNC PCSM 920is a super-state machine and acts as the local orchestrator and messagehandler within an RNC 919. After receiving the RUN command, RNC PCSM 920sends a RUN command to second power control loops 922 a-922 c to begin.Each optical channel 910 a-910 c may be controlled independently and inparallel in second power control loops 922 a-922 c because the opticalchannels 910 a-910 c are individually controlled by a wavelengthselective switch (WSS) upon entering a first ROADM node 924.

RNC PCSM 920 executes each of the second power control loops 922 a-922 cin parallel then aggregates the status of each of the second powercontrol loops 922 a-922 c into a single state and sends the single stateto the L0 power controller 904. L0 power controller 904 maintains asuper-state image of the status of all control loops which the L0 powercontroller 904 does not maintain (indicated by box 924). This way. L0power controller 904 maintains awareness of the status of all elementsin the ROADM optical network 902.

Once second power control 922 a-922 c have completed, the RNC PCSM 920sends a run command to a third power control loop 926. Optical channels910 a-910 c were multiplexed in the WSS of the first ROADM node 924,consequently, a dependency (coupling) between optical channels 910 a-910c was created. As a result, the optical channels 910 a-910 c areprocessed in series until the optical channels 910 a-910 c aredemultiplexed.

Once the third power control loop 926 has completed. RNC PCSM 920 sendsthe status of the third power control loop 926 to the L0 powercontroller 904.

The L0 power controller 904 then sends a RUN command to a TLC PCSM 928to run the next control loops. TLC PCSM 928 communicates a RUN commandto ILA PCSM 934 which executes a fourth power control loop 930. Oncefourth power control loop 930 has completed, ILA PCSM 934 sends a RUNcommand to a fifth power control loop 936. Once the fifth power controlloop 936 has completed, ILA PCSM 934 sends an aggregated status of thefourth and fifth power control loops 934 and 936 to TLC PCSM 928 whichcommunicates the aggregated status to the L0 power controller 904.

The optical signal then passes into a second ROADM node 938 monitored bya second RNC 940. After receiving the aggregated status from TLC PCSM928, L0 power controller 904 sends a RUN command to a second RNC PCSM942 running on the second RNC 940. The second RNC PCSM 942 sends a RUNcommand to a sixth power control loop 944.

Once the sixth power control loop 944 has completed, the second RNC PCSM942 sends a RUN command to seventh power control loops 946 a-946 c.Seventh power control loops 946 a-946 c can be run in parallel becausethe optical channels 910 a-910 c were demultiplexed in the second ROADMnode 938.

The output of the seventh power control loops 946 a-946 c are providedto a RNC PCSM 956 of a third RNC 958 running in a second OLS controller960. The second OLS controller 960 operates in a similar manner to thefirst OLS controller 916. Such operation will not be described herein indetail in the interest of brevity.

Under normal conditions, the L0 power controller 904 will only grantpermission for one control loop (or a parallel group of control loops)to run at a time. The L0 power controller 904 then waits a predefinedperiod of time for the control loop to complete the action beforeallowing another control loop to begin. However, it should be noted thata power controller can abort any running control loop by sending anABORT request. For instance, if a PCSM in an upstream span sends arequest for attention, the power controller can send an ABORT request tothe currently running control loop. The currently running control loopis gracefully stopped and notification is sent to the higher levelcontroller. After receiving the notification, the higher levelcontroller can send a signal to the PCSM that requested attention to RUNa control loop to evaluate the problem.

CONCLUSION

Currently, optical transport systems use serial mechanisms for pathrecovery; however, these serial mechanisms are time consuming to restorethe optical path. In accordance with the present disclosure, methods andapparatus are described for providing a SDN L0 network controller 24monitoring all of the optical nodes 22 and activating a restore path ina parallel manner, thereby reducing the time for restoring connectivityonce a fault has been detected in a working connection.

The foregoing description provides illustration and description, but isnot intended to be exhaustive or to limit the inventive concepts to theprecise form disclosed. Modifications and variations are possible inlight of the above teachings or may be acquired from practice of themethodologies set forth in the present disclosure.

Also, certain portions of the implementations may have been described as“components” or “circuitry” that perform one or more functions. The term“component” or “circuitry” may include hardware, such as a processor, anapplication specific integrated circuit (ASIC), or a field programmablegate array (FPGA), or a combination of hardware and software.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the disclosure. In fact, many of these features may becombined in ways not specifically recited in the claims and/or disclosedin the specification. Although each dependent claim listed below maydirectly depend on only one other claim, the disclosure includes eachdependent claim in combination with every other claim in the claim set.

No element, act, or instruction used in the present application shouldbe construed as critical or essential to the invention unless explicitlydescribed as such outside of the preferred embodiment. Further, thephrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise.

What is claimed is:
 1. A method comprising the steps of: receiving, bycircuitry of a software defined network L0 network controller, firstnetwork performance information of a transport network having a firstpath through the transport network including a first ROADM node, asecond ROADM node and an optical transmission line establishing opticalcommunication between a first degree of the first ROADM node and asecond degree of the second ROADM node, the optical transmission lineincluding an in-line amplifier node having a total input power and atotal output power, the in-line amplifier node having a first monitoringtool configured to measure input optical power of the in-line amplifiernode, and a second monitoring tool configured to measure output opticalpower of the in-line amplifier node; streaming the input optical powerand the output optical power measured by the first and second monitoringtools, respectively, from the in-line amplifier node to the softwaredefined network L0 controller; and configuring, by the software definednetwork L0 network controller, at least one of a gain and a gain tilt ofthe in-line amplifier node, wherein the step of streaming the measuredinput optical power and the measured output optical power by the firstand second monitoring tools, respectively, includes indirectly streamingto the software defined network L0 power controller by streaming themeasured input optical power and the measured output optical power tothe first ROADM node.
 2. The method of claim 1, wherein the in-lineamplifier node is a first in-line amplifier node, and wherein theoptical transmission line includes a second in-line amplifier nodelocated in a series configuration with the first in-line amplifier node,the second in-line amplifier node having a third monitoring toolconfigured to measure input optical power of the second in-lineamplifier node, and a fourth monitoring tool configured to measureoutput optical power of the second in-line amplifier node, and furthercomprising the step of streaming optical power measured by the third andfourth monitoring tools to the software defined network L0 powercontroller.
 3. The method of claim 1, wherein the software definednetwork L0 network controller is programmed with a first control loopmonitoring the optical power measured by the first monitoring tool, anda second control loop monitoring the optical power measured by thesecond monitoring tool.
 4. The method of claim 3, wherein the firstcontrol loop and the second control loop are heirarchial related withinthe software defined network L0 network controller based upon adependency matrix, the hierarchy determining the sequence of executionof the first control loop and the second control loop.
 5. The method ofclaim 3, wherein the first control loop and the second control loop arerun in parallel due to a lack of direct dependency between the firstcontrol loop and the second control loop.
 6. A method comprising thesteps of: receiving, by circuitry of a software defined network L0network controller, first network performance information of a transportnetwork having a first path through the transport network including afirst ROADM node, and a second ROADM node and an optical transmissionline establishing optical communication between a first amplifier of afirst degree of the first ROADM node and a second degree of the secondROADM node, the first ROADM node having a monitoring tool configured tomeasure channel power transmitted through the first degree of the firstROADM node; streaming, with a streaming service based on IP overEthernet over an optical supervisory channel, the channel power measuredby the monitoring tool to the software defined network L0 controller;and configuring, by the software defined network L0 network controller,a gain of the first amplifier.
 7. The method of claim 6, wherein themonitoring tool measures channel power for each channel transmittedthrough the first degree of the first ROADM node.
 8. The method of claim6, wherein the monitoring tool is a first monitoring tool, and whereinthe second ROADM node has a second monitoring tool configured to measurechannel power transmitted through the second degree of the second ROADMnode, and further comprising the steps of streaming the channel powertransmitted through the second degree of the second ROADM node to thesoftware defined network L0 network controller, and configuring, by thesoftware defined network L0 network controller, a gain of a secondamplifier within the second ROADM node.
 9. The method of claim 6,wherein the monitoring tool is a first monitoring tool, and wherein thesecond ROADM node has a second monitoring tool configured to measurechannel power transmitted through the second degree of the second ROADMnode, and wherein the software defined network L0 network controller isprogrammed with a first control loop monitoring the optical powermeasured by the first monitoring tool, and a second control loopmonitoring the optical power measured by the second monitoring tool. 10.The method of claim 9, wherein the first control loop and the secondcontrol loop are heirarchial related within the software defined networkL0 network controller based upon a dependency matrix, the hierarchydetermining the sequence of execution of the first control loop and thesecond control loop.
 11. The method of claim 9, wherein the firstcontrol loop and the second control loop are run in parallel due to alack of direct dependency between the first control loop and the secondcontrol loop.
 12. An optical network, comprising: a first ROADM nodehaving a first degree; a second ROADM node having a second degree; anoptical transmission line establishing optical communication between thefirst degree of the first ROADM node and the second degree of the secondROADM node, the optical transmission line including an in-line amplifiernode having a total input power and a total output power, the in-lineamplifier node having a first monitoring tool configured to measureinput optical power of the in-line amplifier node, and a secondmonitoring tool configured to measure output optical power of thein-line amplifier node; and a software defined network L0 networkcontroller having circuitry configured to receive, via a streamingservice based on IP over Ethernet over an optical supervisory channel,the optical power measured by the first and second monitoring tools fromthe in-line amplifier node, and to configure at least one of a gain anda gain tilt of the in-line amplifier node.
 13. The optical network ofclaim 12, wherein the in-line amplifier node is a first in-lineamplifier node, and wherein the optical transmission line includes asecond in-line amplifier node located in a series configuration with thefirst in-line amplifier node, the second in-line amplifier node having athird monitoring tool configured to measure input optical power of thesecond in-line amplifier node, and a fourth monitoring tool configuredto measure output optical power of the second in-line amplifier node,and wherein the software defined network L0 network controller receivesoptical power measured by the third and fourth monitoring tools.
 14. Theoptical network of claim 12, wherein the software defined network L0network controller is programmed with a first control loop monitoringthe optical power measured by the first monitoring tool, and a secondcontrol loop monitoring the optical power measured by the secondmonitoring tool.
 15. The method of claim 14, wherein the first controlloop and the second control loop are heirarchial related within thesoftware defined network L0 network controller based upon a dependencymatrix, the hierarchy determining the sequence of execution of the firstcontrol loop and the second control loop.
 16. The method of claim 14,wherein the first control loop and the second control loop are run inparallel due to a lack of direct dependency between the first controlloop and the second control loop.